CPAP is a well known treatment for the temporary relief of conditions including obstructive sleep apnea (OSA) and snoring. By this technique, air (or other breathable gas) at a pressure elevated above atmospheric pressure is constantly supplied to the entrance to a patient's airway (by the nasal and/or oral route) by means of known arrangements of masks or nasal prongs. The elevated air pressure acts as a pneumatic splint of the patient's airway in the vicinity of the oro- and hypo-pharynx, reducing or eliminating the occurrences of apneas or hypopneas during sleep. A bi-level CPAP device delivers two distinct pressures during the patient's respiratory cycle; a relatively lower pressure during exhalation and a relatively higher pressure during inhalation. An automatically adjusting CPAP device may operate to provide a relatively low background pressure which increases to a therapeutic pressure on a needs basis, and preferably at a time to prevent the onset of an apnea.
Assisted respiration similarly provides a supply of air (or other breathable gas) at a pressure elevated above atmospheric pressure, although is concerned more with providing a sufficient flow of air (or other breathable gas), rather than regulating the pressure of air to a continuous (constant) level in the case of CPAP treatment.
In recent times, CPAP apparatus have been constituted by a nose and/or mouth mask coupled by a flexible air (or other breathable gas) delivery tube to a controllable flow generator. The flow generator includes a speed-controlled brushless DC motor connected with a fixed vane turbine. Control of the CPAP treatment pressure delivered to a patient's airway is conducted at the flow generator by speed control of the motor in response to signals issued by a microprocessor.
Whilst this arrangement provides satisfactory treatment of conditions such as OSA and snoring, it is desirable for alternative arrangements to be devised that can remove the pressure controls from the remote flow generator to being at or near the patient mask. This may lead to a reduction of the cost of CPAP treatment apparatus by removing the need for a power supply, microprocessor controller, motor and turbine. A practical concern in such an arrangement is that the mask not be made too heavy so as to disturb the patient in wearing the mask during sleep. Prior art delivery pressure controls located at a mask, such as breathing apparatus worn by military pilots, are heavy and cumbersome and not suitable to being worn during sleep when a patient's neck and shoulder muscles necessarily need to be in a relaxed state.
It is an object of the present invention to provide delivery pressure control apparatus that can be incorporated at or near a patient mask and that is not uncomfortable or cumbersome to the patient when worn during sleep.